Active matrix organic light-emitting display and display apparatus

ABSTRACT

An AMOLED comprises a plurality of pixel structures arranged in a matrix and one layer of power supply signal electrode configured to provide a power supply voltage signal for the pixel structures, and the power supply signal electrode has a planar structure. The planar power supply signal electrode can greatly reduce its resistance and hence can reduce the IR drop of power supply voltage signals that are transmitted over the power supply signal electrode, effectively reduce the impact of the IR drop on the display effect, and remarkably reduce the power consumption of a panel.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from Chinese National Application No.201210387817.X filed on Oct. 12, 2012, the contents of which areincorporated herein by reference.

BACKGROUND

Embodiments of the present disclosure relate to an organiclight-emitting display (OLED) and a display apparatus.

An organic light-emitting display (OLED) is a display in which organicsemiconductor luminescent materials are driven by an electric field toemit light through carrier injection and recombination. The luminescentmechanism of an OLED is as follows: an indium tin oxide (ITO)transparent electrode and a metal electrode are employed as an anode anda cathode of the display; and electrons and holes are driven under acertain voltage to be injected into an electron transport layer and ahole transport layer from the anode and the cathode, migrated from theelectron transport layer and the hole transport layer to an lightemitting layer, and meet each other in the light emitting layer to formexcitons which are hence excited to emit visible light through radiativerelaxation. The OLED has the advantages of thinner thickness and lighterweight, initiative luminescence (no backlight required), wide viewingangle, high resolution, high brightness, fast response, low powerconsumption, wide range of service temperature, excellent shockresistance, low cost, capability of achieving flexible display, and thelike.

There are two types of OLEDs in the light of the driving mode: passivedriving mode and active driving mode, i.e., direct addressing mode andthin-film transistor (TFT) matrix addressing mode. The active drivingmode refers to that each light-emitting element in an active matrix (AM)is independently controlled through TFT addressing. A pixel structurecomprising the light-emitting element and a thin film transistor (TFT)addressing circuit is loaded with direct-current supply voltage signals(VDD) from a power supply signal line for driving.

The wiring mode of the power supply signal lines in a current AMOLEDpanel is, as illustrated in FIG. 1, as follows: in general, power supplysignal lines corresponding to pixel structures one by one are disposedamong each column of pixel structures; a closed peripheral power supplysignal line circle is disposed outside and around the display area ofthe panel; and direct-current supply voltage signals (VDD) from a signalsource IC are respectively transmitted to the pixel structures connectedtherewith through the power supply signal lines.

Another wiring mode of the power supply signal lines is illustrated inFIG. 2. Compared with the wiring mode as illustrated in FIG. 1, in thewiring mode as illustrated in FIG. 2, power supply signal lines areadditionally disposed between any two adjacent rows of pixel structures;and the additionally provided transverse wiring power supply signallines and the longitudinal power supply signal lines are cross-connectedwith each other to form a netted structure, which is further integrallyconnected with the peripheral power supply signal line circle disposedoutside the display area. This wiring mode can effectively reduce the IRdrop of the direct-current supply voltage signals transmitted over thepower supply signal lines, and hence reduce the power consumption of theAMOLED panel and alleviate the impact of the IR drop on the displayeffect.

Although the above wiring mode of the power supply signal lines caneffectively reduce the impact of the IR drop of the power supply signallines on the display effect and reduce the power consumption of thepanel when applied to a small-size AMOLED, along with the increased sizeof the AMOLED, the above wiring mode of the power supply signal linescannot effectively solve the problems of the impact of the IR drop onthe display effect and the power consumption of the panel.

SUMMARY

Embodiments of the present disclosure provide an AMOLED and a displayapparatus, capable of effectively reducing the impact of the IR drop ofpower supply signal lines on the display effect and the powerconsumption of a panel.

In one aspect, the present disclosure provides an AMOLED, whichcomprises a plurality of pixel structures arranged in a matrix and onelayer of power supply signal electrode configured to provide a powersupply voltage signal for the pixel structures, and the power supplysignal electrode has a planar structure.

In another aspect, the present disclosure provides a display apparatus,which comprises the AMOLED provided by the embodiment of the presentdisclosure.

In the AMOLED and the display apparatus provided by the embodiments ofthe present disclosure, the planar power supply signal electrode cangreatly reduce its resistance thereof and hence reduce the IR drop ofthe power supply voltage signals that are transmitted over the powersupply signal electrode, effectively reduce the impact of the IR drop onthe display effect, and remarkably reduce the power consumption of thepanel.

Further scope of applicability of the present disclosure will becomeapparent from the detailed description given hereinafter. However, itshould be understood that the detailed description and specificexamples, while indicating preferred embodiments of the disclosure, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the disclosure will becomeapparent to those skilled in the art from the following detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure will become more fully understood from thedetailed description given hereinafter and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present disclosure and wherein:

FIG. 1 is a first schematic structural wiring diagram of the powersupply signal lines in a traditional AMOLED;

FIG. 2 is a second schematic structural wiring diagram of the powersupply signal lines in a traditional AMOLED;

FIG. 3 is a schematic structural view of an AMOLED panel having a powersupply signal electrode, provided by an embodiment of the presentdisclosure;

FIG. 4 is a schematic structural view of a pixel structure in the AMOLEDprovided by an embodiment of the present disclosure;

FIGS. 5a and 5b are schematic diagrams illustrating the position of thepower supply signal electrode of the AMOLED provided by an embodiment ofthe present disclosure;

FIGS. 6 and 7 are schematic structural views of an AMOLED panel having apower supply signal electrode and electrode signal lines, provided by anembodiment of the present disclosure; and

FIG. 8 is a schematic structural view of a low-level signal electrode inthe AMOLED provided by an embodiment of the present disclosure.

DETAILED DESCRIPTION

The preferred embodiments of the AMOLED and the display apparatusprovided by the present disclosure are described in detail below withreference to the accompanying drawings. The thickness of the variousfilms and the size of the various areas in the accompanying drawings arenot drawn in actual scale but are only intended to illustrate theembodiments of the present disclosure.

The AMOLED provided by an embodiment of the present disclosure, asillustrated in FIG. 3, comprises a plurality of pixel structuresarranged in a matrix and further comprises one layer of power supplysignal electrode configured to provide a power supply signal for thepixel structures, and the power supply signal electrode has a planarstructure; each pixel structure is, for instance, a pixel for emittingred, green or blue light; and the planar power supply signal electrodecovers two or more than two pixel structures at the same time, and evencorresponds to all the pixel structures of the whole AMOLED.

In the AMOLED provided by the above embodiment of the presentdisclosure, the traditional linear power supply signal lines aremodified (redesigned) and optimized, and converted into one layer ofplanar power supply signal electrode, by which a display area of thepanel is covered in the whole plane for example. In comparison, thewhole planar power supply signal electrode can greatly reduce theresistance thereof and hence reduce the IR drop of the power supplyvoltage signals that are transmitted over the power supply signalelectrode, effectively reduce the impact of the IR drop on the displayeffect, and remarkably reduce the power consumption of the panel.

The typical structures of the pixel structure and the power supplysignal electrode of the AMOLED are described in detail below.

For instance, one pixel structure in the AMOLED generally comprises anupper substrate, a lower substrate, and a buffer layer, a thin filmtransistor (TFT) structure and an organic electroluminescent (EL)structure disposed on a lower substrate in order, as illustrated in FIG.4, and the TFT structure is configured to drive the organic ELstructure. The TFT structure, for instance, includes an active layer, agate insulating layer, a gate electrode, a protective layer, source anddrain electrodes, and a first insulating layer. In addition, the TFTstructure may be in a traditional top-gate structure, a traditionalbottom-gate structure, or the like, and any of the embodiments of thepresent disclosure will not be limited thereto.

The simplest organic EL structure includes an anode, an organiclight-emitting layer and a cathode. In order to improve the luminousefficiency, one example of the organic EL structure may comprise ananode (e.g., a pixel electrode for a pixel structure), an edgeprotective layer, a hole transport layer, an organic light-emittinglayer, an electron transport layer, and a cathode. Moreover, the organicEL structure may further comprise functional film layers such as anelectron barrier layer and a hole barrier layer. These structural layersmay be made of a material (or materials) known in the art and will notbe described in detail herein for simplicity.

The traditional linear power supply signal lines are generally disposedon the same layer as the source/drain electrodes, namely the powersupply signal lines and the source/drain electrodes are formed in onepatterning process. In the AMOLED provided by the embodiment of thepresent disclosure, the power supply signal lines are redesigned intothe planar power supply signal electrode. Moreover, in order to notaffect the normal operation of the pixel structures, for instance, thepower supply signal electrode may be arranged between the lowersubstrate and the buffer layer for forming each pixel structure, asillustrated in FIG. 5a , or may be arranged between the organic ELstructure and the upper substrate, for instance, between the cathode andthe upper substrate, and isolated from the cathode through a secondinsulating layer, as illustrated in FIG. 5 b.

The AMOLED provided by the embodiment of the present disclosure may beof a top emission type AMOLED or a bottom emission type AMOLED. In orderto reduce the resistance, the power supply signal electrode is usuallymade of a low-resistance metallic material, for instance, is made of anopaque metal. Therefore, in order to not affect the normal emission ofeach pixel structure, when the pixel structure is of the bottom emissiontype and the power supply signal electrode is disposed between thebuffer layer and the lower substrate, as illustrated in FIG. 5a , apattern in which the power supply signal electrode is removed (or notformed) in an area A of the power supply signal electrode (i.e., anopening in the planar structure) is formed, corresponding to alight-emitting window of each pixel structure, so that the light excitedby the organic light-emitting layer can be normally emitted out throughthe light-emitting window.

Similarly, when each pixel structure is of the top emission type and thepower supply signal electrode is disposed between the cathode and theupper substrate, as illustrated in FIG. 5b , a pattern in which thepower supply signal electrode is removed (or not formed) in the area Aof the power supply signal electrode (i.e., the opening in the planarstructure) is formed, corresponding to the light-emitting window of eachpixel structure, so that the light excited by the organic light-emittinglayer can be normally emitted through the light-emitting window.

As the power supply signal electrode is not arranged in all the filmlayers of the pixel structures, in order to realize that the powersupply signal electrode can normally provide the power supply voltagesignals for the pixel structures, for instance, the power supply signalelectrode may be electrically connected with the active layer and one ofthe source/drain electrodes in the TFT structures, or with the pixelelectrode in the organic EL structure via a through hole. For example,as illustrated in FIG. 5a , the power supply signal electrode isarranged between the lower substrate and the buffer layer andelectrically connected with the active layer via a through hole; and asillustrated in FIG. 5b , the power supply signal electrode is disposedbetween the upper substrate and the cathode and electrically connectedwith the pixel electrode via a through hole. Please note FIGS. 5a and 5bonly illustrate the connection relationships between the power supplysignal electrode and various film layers in the pixel structures. Theembodiments of the present disclosure are not limited thereto.

The preparation process of the AMOLED of the embodiment is described indetail below by taking the AMOLED structure as illustrated in FIG. 5afor example. An exemplary preparation process specifically comprises thefollowing processes.

1. A metal layer is deposited on a lower substrate (e.g., a bare glasssubstrate), and a pattern of a power supply signal electrode is formedby one patterning process, and such a patterning processes may compriseexposure, development, etching of the metal layer and photoresistremoval.

2. A buffer layer is deposited on the pattern of the power supply signalelectrode, in which the buffer layer, for instance, may be made ofSiNx/SiO2 two-layer structure; and a through hole is formed, via whichthe power supply signal electrode is connected with the active layer ofthe TFT structure to be formed, by one patterning process. Thus, powersupply voltage signals can be transmitted to the active layer of thepixel structure over the power supply signal electrode via the throughhole.

3. For instance, an amorphous silicon semiconductor layer is depositedon the buffer layer, and then a polysilicon (P-Si) is formed after theamorphous silicon of the amorphous silicon semiconductor layer iscrystallized with a low-temperature polysilicon process, and the patternof the active layer is formed by one patterning process.

4. A gate insulating (GI) layer is formed on the pattern of the activelayer, in which the gate insulating layer, for instance, can be made ofSiO₂/SiNx two-layer structure.

5. A gate electrode metal layer is deposited on the gate insulatinglayer, and the pattern of a gate electrode and a gate electrode signalline is formed by one patterning process;

6. An ion doping process is performed on areas of the active layercorresponding to the source/drain electrodes to be formed, with theformed gate electrode being used as a mask layer, and then an ionactivating process is performed.

7. A protective layer (ILD) is formed on the pattern of the gateelectrode and the gate electrode signal line, and a through hole isformed, via which the power supply signal electrode is respectivelyconnected with the active layer and one of the source/drain electrodesto be formed, by one patterning process.

8. A source-drain electrode metal layer is formed on the protectivelayer, and the pattern of the source/drain electrodes and data signalline is formed by one patterning process.

9. A first insulating layers (e.g., SiNx/SiO₂) and a planarizing (PLN)layer are formed on the source-drain electrode metal layer, and the PLNlayer can be formed of a resin material for example. Then, ahydrogenation process is performed to improve the crystallizationcharacteristic of the active layer. A through hole is formed, via whichanother of the source/drain electrodes is connected with the pixelelectrode to be formed, by one patterning process.

10. A pixel electrode layer (ITO) is formed (deposited) on the firstinsulating layer and the planarizing layer, and the pattern of the pixelelectrode is formed by one patterning process.

11. An edge protective layer (PDL), a hole transport layer, an organiclight-emitting layer, an electron transport layer and a cathode areformed on the patterns of the pixel electrodes in order; finally anupper substrate is bonded thereon, and the upper substrate may be aglass or plastic substrate.

Moreover, in order to further reduce the resistance of the power supplysignal electrode, in an AMOLED provided by another embodiment of thepresent disclosure, as illustrated in FIG. 6, the AMOLED furthercomprises power supply signal lines in addition to the planar powersupply signal electrode. The power supply signal lines are connected inparallel with the power supply signal electrode, so that the resistanceof the power supply signal electrode can be further reduced, and hencethe IR drop during the transmission of power supply voltage signals canbe reduced. For instance, the power supply signal lines are disposed onthe same layer with source/drain electrodes in TFT structures of pixelstructures. For example, the power supply signal lines may include powersupply signal lines disposed between any two adjacent columns of pixelstructures and corresponding to the pixel structures one by one, and aclosed peripheral power supply signal line circle is disposed outsidethe display area of a panel. Or, power supply signal lines can beadditionally disposed between any two adjacent rows of pixel structures,and the transverse wiring power supply signal lines and the longitudinalwiring power supply signal lines are cross-connected to form a nettedstructure.

For example, the power supply signal lines can be electrically connectedwith the active layers of pixel structures via through holes, andmoreover, the power supply signal electrode is electrically connectedwith the active layers via through holes, thus the power supply signallines and the power supply signal electrode are combined to form aconduction structure in parallel, as illustrated in FIG. 7. Of course,the power supply signal lines and the power supply signal electrode canalso be combined to form the conduction structure in parallel throughanother specific structure. The embodiments of the present disclosureare not limited thereto.

Furthermore, the AMOLED provided by the embodiment of the presentdisclosure may further comprise at least one layer of low-level signalelectrode (VSS) electrically connected with the cathodes in the organicEL emission layers, and each layer of the low-level signal electrode mayalso have a planar structure. As illustrated in FIG. 8, the low-levelsignal electrode layers 81 can be electrically connected together via athrough hole (or through holes) 82, so that the resistance of thelow-level signal electrodes can be further reduced, and therefore thepower consumption of the VSS can be reduced.

Another embodiment of the present disclosure further provides a displayapparatus, which comprises an AMOLED provided by any embodiment of thepresent disclosure. The display apparatus of the embodiment of thepresent disclosure further comprises other components or devices, suchas driving circuits or signal processing circuits, and the AMOLED can bereferred to the above disclosure.

In the AMOLED and the display apparatus provided by the embodiments ofthe present disclosure, the traditional linear power supply lines aremodified and optimized and converted into one layer of planar powersupply signal electrode in which the display area of the panel can becovered by the whole plane for example. Compared with the linear powersupply signal lines in the traditional AMOLED, the planar power supplysignal electrode can greatly reduce the resistance thereof, and hencereduce the IR drop of the power supply voltage signals that aretransmitted over the power supply signal electrode, effectively reducethe impact of the IR drop on the display effect, and remarkably reducethe power consumption of the panel.

Obviously, various changes and modifications can be made to the presentdisclosure by those skilled in the art without departing from the spiritand scope of the present disclosure. Therefore, if the changes andmodifications of the present disclosure fall within the scope of theappended claims of the present disclosure and equivalent techniquesthereof, the present disclosure is also intended to include the changesand modifications.

What is claimed is:
 1. An active matrix organic light-emitting display (AMOLED), comprising: a plurality of pixel structures arranged in a matrix, wherein each of the pixel structures comprises a thin-film transistor (TFT) structure and an organic electroluminescent (EL) structure, and the TFT structure comprises a source/drain electrode and an active layer and is configured to control the organic EL structure; one layer of power supply signal electrode configured to provide a power supply voltage signal for the pixel structures and directly connected to the active layer of the TFT structure of each of the pixel structures via a first through hole, power supply signal lines extending between at least two pixel structures; wherein the power supply signal electrode has a planar structure, and the power supply signal lines are disposed on the same layer as the source/drain electrode in the TFT structure of each of the pixel structures and directly connected to the active layer of the same TFT structure of each of the pixel structures via a second through hole as the power supply signal electrode is directly connected to, whereby the power supply signal lines are connected in parallel with the power supply signal electrode upon the TFT structure of each of the pixel structures being turned on.
 2. The display according to claim 1, wherein each of the pixel structures comprises an upper substrate, a lower substrate and a buffer layer, the thin-film transistor (TFT) structure and the organic electroluminescent (EL) structure disposed on the lower substrate in order.
 3. The display according to claim 2, wherein the power supply signal electrode is disposed between the buffer layer and the lower substrate.
 4. A display apparatus, comprising the AMOLED according to claim
 1. 